Spring having cam means to vary the bias thereon



Nov. 9, v1965 E. HAlDERER SPRING HAVING CAM MEANS TO VARY THE BIAS THEREON Filed Nov. 7, 1962 2 Sheets-Sheet 1 u ilw Wand/07K M fifforne .s

Nov. 9-, 1965 E. HAIDERER SPRING HAVING CAM MEANS TO VARY THE BIAS THEREON Filed NOV. 7, 1962 PRESSURE H INITIAL PRESSURE u FINAL PRESSURE asssuna P INITIAL PRESSURE FINAL PRESSURE 2 Sheets-Sheet 2 WALL THICKNESS IN VEN TOR. Emm /obi f/mberer BY W,M*M 1777014155 United States Patent Office 3,216,715 Patented Nov. 9, 1965 3,216,715 SPRING HAVING CAM MEANS T VARY THE BIAS THEREON Emmerich Haiderer, St. Polten, Austria, assiguor to J. M.

Voith Aktieugesellschaft, St. Polten, Austria, a corporation of Austria Filed Nov. 7, 1962, Ser. No. 236,021 Claims priority, application Austria, Nov. 10, 1961,

8 Claims. (Cl. 267--1) This invention relates to a spring and means to vary the bias thereon in a pressure regulating device for machines for making asbestos cement pipes, which device serves for adjusting the pressure applied to the mandrel roll according to a predetermined course of pressure development which course depends from the wall thickness of the ,pipe being wound, said device comprising a springloaded relief valve and a hydraulic servomotor with variable speed to adjust the bias of the spring.

In the manufacture of asbestos cement pipes a fleece of asbestos cement is accumulated layer by layer on a mandrel until a desired wall thickness is reached. While the fleece is thus wound, the mandrel and the pipe being formed are pressed against the breast roll. With the growing wall thickness the pressure must be varied depending on the desired properties of the pipe and the material being used. In most cases the pressure must be lowered from a maximum pressure to a minimum pressure along a certain predetermined curve.

Pressure may be applied to the mandrel from above by a pressure carriage which holds press rolls, back-up rolls for same, and hydraulic cylinders. When the winding operation is about to begin the cylinders are filled with oil and the pressure carriage is lowered and locked in a position where the press rolls rest on the mandrel. As soon as the winding actually begins the press rolls are raised by the increasing pipe diameter and oil is displaced from the pressure cylinders and flows through a relief valve to an oil container.

In known machines this relief valve is either controlled by hand, or by means of a thickness gauge which measures the pipe wall, or by means of a variable speed drive directly proportional to the winding time.

It is an object of the invention to provide a spring having a simple and reliable automatic device to regulate the bias on the spring for use in a pressure regulator which device can easily be adjusted for a Wide range of maximum and minimum pressures and which will vary the pressure along any desired course between them; which allows rising and falling pressure courses; which can hold a plurality of pressure course programs side by side and thus facilitates quick changes by simply sliding the relief valve from one curve to another; which returns to the ready position at much higher speed than the operating stroke; which is independent of a thickness gauge; and which needs no mechanical connections to the control desk.

A specific embodiment of the invention is shown diagrammatically in FIG. 1 at the beginning of the winding operation. The left-hand part of the figure shows the Winding device and particularly the pressure applying device on a smaller scale than the control device on the right-hand side of the figure.

FIGURES 2 to 4 show some settings of the pressure variation cam means and the associated pressure applied in relation to the wall thickness.

A fleece 22, formed by means of a sieve cylinder, is fed to the mandrel 4. A lower belt 24 running around the breast roll 23 supports the fleece 22. The upper belt 25 distributes the pressure on the mandrel 4. Pressure is applied to the mandrel 4 by means of back-up rolls 2 and press rolls 3. The initial pressure in the hy- Zdrel. As soon as the winding operation begins, oil is displaced from the pressure cylinders 27 and discharged through the conduit 1 and the relief valve 5 into the conduit 12. This relief valve 5 has a leak oil bore 5' and is spring-loaded. The pressure in the pressure cylinders 27 is controlled by the bias of spring 6, which bias is determined by the position of the feeler roll 7 along which an adjustable cam means (pressure variation cam) 8 is moving. The feeler roll 7 is mounted on the telescopic housing 6" and is held against the cam means 8 by a spring 6'. This pressure variation cam means 8 is moved by the differential piston 9, 9' of a hydraulic servomotor.

In the position shown in the drawing, i.e. before the beginning of the winding operation, the solenoid operated three-way valve 11 is positioned to apply pressure from supply-conduit-28 to both faces 9", 9"'- of the differential piston 9 so that the latter is urged into its left-hand end position. The direction of flow in this phase is indicated by arrows a.

When the winding actually begins the solenoid 11" is deenergized by push button control and the spring 11 positions the valve 11 so that the piston surface 9" is connected via the variable resistance 10 to the discharge conduit 17 and to the container 13 (arrows c). The smaller piston surface 9" is constantly under the pressure prevailing in conduit 28 and communicates to the pressure oil container or the oil pump. The variable resistance 10 must be so adjusted that the time required for the full stroke of piston 9 is equal to the time required to Wind one pipe. The pressure variation cam means 8 is mounted adjustably on the rod of piston 9, 9'.

Said pressure variation cam means 8 consists of the horizontal initial section 8a, the horizontal final section and a ruler 8b. This ruler 8b is pivoted at 19 to the cam block 18a and has preferably a guide slot 21 which links it to a projecting pin 20, or the like on the other cam block 180.

The two cam blocks 18a, 18c can be adjusted independently in horizontal and vertical directions.

The vertical adjustment of cam blocks 18a sets the initial pressure of the system and is effected by means of the adjusting screw 14. The final pressure is determined by the vertical adjustment of cam block 180 by means of the adjusting screw 15. The independent horizontal adjustment of cam blocks 18a and 18c is eflected by adjusting-wheels 15a, 16a, bevel gears 15b, 16b, and screws 15c, respectively and accounts for the length of time for which the constant initial and final pressures will be held.

This makes it possible, for instance, to maintain a constant initial pressure for the first 35% of the winding time, then lower the pressure uniformly to the final pres sure which is then maintained constant for the last 30% of the winding time.

The time for the uniform decrease can be extended in both directions by moving cam blocks 18a, 18c apart horizontally until ultimately it covers the entire winding time and the pressure will not be held constant at all.

FIGURES 2 to 4 show settings of the pressure variation cam means and the associated pressure p in relation to the wall thickness s. The initial and final pressures and the periods of constant pressures can be read directly from suitable dials.

What is claimed is:

1. Means for varying the bias of the spring in a spring loaded relief valve of a pressure regulating device comprising a housing, spring means mounted in said housing,

a hydraulic servomotor having a piston and piston rod, means for supplying a constant pressure fluid to said piston and a restricted exhaust of fluid from said piston to move said piston rod at a predetermined constant forward speed, pressure variation cam means adjustably mounted on said piston rod and movable therewith, and feeler means cooperating with said cam means and operatively connected to said spring to adjust the bias thereof in response to the movement of said carnmeans.

2. Means as set forth in claim 1, in which said pressure variation cam means comprises a straight initial section for maintaining a constant pressure setting of said spring, and a straight final section for maintaining a constant pressure setting of said spring.

3. Means as set forth in claim 2, in which said pressure variation cam means comprises a straight intermediate section between said initial and final sections.

4. Means as set forth in claim 2, in which said pressure variation cam means comprises two cam blocks secured to said piston rod and adapted'to be mutually independently adjustable relative thereto in horizontal and vertical directions, means for fixing said cam blocks in adjusted positions to said piston rod, said cam blocks respectively having underside surfaces arranged to cooperate with said feeler means during initial and final sec:

tions of said movement, said cam means further comprising a ruler, which is pivoted to one of said two blocks and has an underside arranged to cooperate with said feeler means during an intermediate section of said movement between said initial and final sections.

5. Means as set forth in claim 4, which comprises adjusting screws for adjusting said cam blocks.

6. Means as set forth in claim 4, which comprises adjusting transmissions for adjusting said cam blocks.

7. Means as set forth in claim 4, in which the other of said cam blocks carries a projection and said ruler is formed with a guide slot cooperating with said projection.

8. Means as set forth in claim 7, in which said projection is a pin.

References Cited by the Examiner UNITED STATES PATENTS 989,543 4/11 Geissinger 251 1,343,735 6/20 MacBryde l37530 2,735,669 2/56 Seiler.

3,029,060 4/62 Anderson 251-14 ISADOR WEIL, Primary Examiner. 

1. MEANS FOR VARYING THE BIAS OF THE SPRING IN A SPRING LOADED RELIEF VALVE OF A PRESSURE REGULATING DEVICE COMPRISING A HOUSING, SPRING MEANS MOUNTED IN SAID HOUSING, A HYDRAULIC SERVOMOTOR HAVING A PISTON AND PISTON ROD, MEANS FOR SUPPLYING A CONSTANT PRESSURE FLUID TO SAID PISTON AND A RESTRICTED EXHAUST OF FLUID FROM SAID PISTON TO MOVE SAID PISTON ROD AT A PREDETERMINED CONSTANT FORWARD SPEED, PRESSURE VARIATION CAM MEANS ADJUSTABLY MOUNTED ON SAID PISTON ROD AND MOVABLE THEREWITH, AND FEELER MEANS COOPERATING WITH SAID CAM MEANS AND OPERATIVELY CONNECTED TO SAID SPRING TO ADJUST THE BIAS THEREOF IN RESPONSE TO THE MOVEMENT OF SAID CAM MEANS. 